Two-component coating system

ABSTRACT

The present invention relates to a two-component coating system comprising a first component and a second component each of which is separate and distinct from each other, wherein the first component comprises a carboxylic acid functional polymer dissolved and/or dispersed in an aqueous medium, and the second component comprises a multi-aziridine compound having: a) from 2 to 6 of the following structural units (A): b) whereby m is an integer from 1 to 8; and o R′ and R″ are both H b) one or more linking chains wherein each one of these linking chains links two of the structural units A; c) one or more connecting groups whereby each one of the connecting groups connects two of the structural units A; and d) a molecular weight in the range from 840 Daltons to 5000 Daltons, wherein the molecular weight is measured using MALDI-TOF mass spectrometry.

The present invention relates to two-component coating systemscomprising a first component and a second component each of which isseparate and distinct from each other, wherein the first componentcomprises a carboxylic acid functional polymer dissolved and/ordispersed in an aqueous medium, and the second component comprises amulti-aziridine compound, whereby the first and second component areseparately stored, since the crosslinking reaction between thecrosslinking agent and the polymer to be crosslinked may startimmediately after mixing the crosslinking agent with the aqueouscomposition of polymer to be crosslinked.

Over the years, the need for coatings with improved resistances, likestain and solvent resistance, improved mechanical properties andimproved adhesive strength is more and more growing. One or more ofthose properties can be elevated to a higher level by means ofcrosslinking. Many crosslink mechanisms have been studied over the yearsand for waterborne dispersions, the most useful ones include isocyanatecrosslinking of hydroxyl functional dispersions, the reaction betweencarbodiimide and carboxylic acid, epoxy crosslinking and crosslinkingusing aziridine based crosslinkers.

U.S. Pat. No. 5,133,997 describes coating compositions comprising anaqueous dispersion of linear aliphatic urethane resins, an anionicsurfactant and a crosslinking agent capable of facilitating the cure ofsaid resin. Trimethylolpropane tris(2-methyl-1-aziridinepropionate), CASnumber 64265-57-2, a polyfunctional aziridine crosslinker, is used ascrosslinking agent, which is a well-known and very active forcrosslinking carboxylic acid functional polymers. This crosslinkerhowever has an unfavourable genotoxic profile. There is a need in theindustry to improve the safety, health and environmental profile ofadhesives, inks and coatings and also of the substances used forpreparing adhesives, inks and coatings. Genotoxicity describes theproperty of chemical or physical agents that cause any type of DNAdamage, which may not always lead to a transmittable mutation.Mutagenicity refers to the induction of permanent transmissible DNAchanges (as DNA composition or chromosome structure), which are retainedin somatic cell division and passed onto progeny in germ cells.Genotoxicity must not be confused with mutagenicity. All mutagens aregenotoxic whereas not all genotoxic substances are mutagenic.

The object of the present invention is to provide a two-componentcoating system comprising a first component and a second component eachof which is separate and distinct from each other, wherein the firstcomponent comprises a carboxylic acid functional polymer dissolvedand/or dispersed in an aqueous medium, and the second componentcomprises a compound with at least two aziridinyl groups which hasreduced genotoxicity compared to trimethylolpropanetris(2-methyl-1-aziridinepropionate) and with good crosslinkingefficiency. Compounds with at least two aziridinyl groups are furtherreferred herein as multi-aziridine compounds.

This object has surprisingly been achieved by providing a two-componentcoating system comprising a first component and a second component eachof which is separate and distinct from each other, wherein

the first component comprises a carboxylic acid functional polymerdissolved and/or dispersed, preferably dispersed, in an aqueous medium,andthe second component comprises a multi-aziridine compound having:

-   a) from 2 to 6 of the following structural units (A):

-   -   whereby    -   m is an integer from 1 to 6, and    -   R′ and R″ are both H;

-   b) one or more linking chains wherein each one of these linking    chains links two of the structural units A;

-   c) one or more connecting groups whereby each one of these    connecting groups connects two of the structural units A and whereby    the connecting groups preferably consist of at least one    functionality selected from: aliphatic hydrocarbon functionality,    cycloaliphatic hydrocarbon functionality, aromatic hydrocarbon    functionality, isocyanurate functionality, iminooxadiazindione    functionality, ether functionality, ester functionality, amide    functionality, carbonate functionality, urethane functionality, urea    functionality, biuret functionality, allophanate functionality,    uretdione functionality and any combination thereof; and

-   d) a molecular weight in the range from 840 Daltons to 5000 Daltons.

It has surprisingly been found that these multi-aziridine compounds havereduced genotoxicity compared to trimethylolpropanetris(2-methyl-1-aziridinepropionate). The multi-aziridine compoundsaccording to the invention show either only weakly positive inducedgenotoxicity or even they do not show genotoxicity, i.e. they show agenotoxicity level comparable with the naturally occurring background.

The genotoxicity can be measured by the ToxTracker® assay (Toxys,Leiden, the Netherlands) as further described herein. The ToxTracker®assay can be applied for pure substances or for compositions which arethe direct products obtained in the preparation of the multi-aziridinecompounds of the invention. With positive induced genotoxicity is meantthat the induction level of the biomarkers Bscl2-GFP and Rtkn-GFP isequal to or higher than 2-fold at at least one of 10, 25 and 50%cytotoxicity in the absence or presence of the metabolizing system ratS9 liver extract. With weakly positive induced genotoxicity is meantthat the induction level of the biomarkers Bscl2-GFP and Rtkn-GFP ishigher than 1.5-fold and lower than 2-fold at at least one of 10, 25 and50% cytotoxicity (but lower than 2-fold at 10, 25 and 50% cytotoxicity)in the absence or presence of rat S9 liver extract-based metabolizingsystems (aroclor1254-induced rats, Moltox, Boone, N.C., USA). Withgenotoxicity comparable with the naturally occurring background is meantthat the induction level of the biomarkers Bscl2-GFP and Rtkn-GFP isless than or equal to 1.5-fold at 10, 25 and 50% cytotoxicity in theabsence and presence of rat S9 liver extract-based metabolizing systems(aroclor1254-induced rats, Moltox, Boone, N.C., USA). The inductionlevel of the genotoxicity reporters Bscl2-GFP and Rtkn-GFP is preferablyless than or equal to 1.5-fold at 10, 25 and 50% cytotoxicity in theabsence and presence of rat S9 liver extract-based metabolizing systems(aroclor1254-induced rats, Moltox, Boone, N.C., USA). A substanceshowing an induction level less than or equal to 1.5-fold at 10, 25 and50% cytotoxicity in the absence and presence of rat S9 liverextract-based metabolizing systems (aroclor1254-induced rats, Moltox,Boone, N.C., USA) is not genotoxic.

U.S. Pat. No. 3,523,750 describes a process for modifying proteinaceoussubstrates such as wool with a multi-aziridine compound. U.S. Pat. No.5,258,481 describes multifunctional water-dispersible crosslink agentswhich is an oligomeric material containing carbodiimide functionalitiesand reactive functional groups which are different from saidcarbodiimide functional group. U.S. Pat. No. 5,359,005 describesone-package coating compositions comprising at least one polymer and/oroligomer having a molecular weight of at least about 100 and bearing atleast two aziridine moieties, at least two carbodiimide moieties orcombinations thereof and at least one polymer and/or oligomer bearing atleast two covalently blocked carboxylic acid moieties.

For all upper and/or lower boundaries of any range given herein, theboundary value is included in the range given, unless specificallyindicated otherwise. Thus, when saying from x to y, means including xand y and also all intermediate values.

The term “coating composition” encompasses, in the present description,paint, coating, varnish, adhesive and ink compositions, without thislist being limiting. The term “aliphatic hydrocarbon group” refers tooptionally branched alkyl, alkenyl and alkynyl group. The term“cycloaliphatic hydrocarbon group” refers to cycloalkyl and cycloalkenylgroup optionally substituted with at least one aliphatic hydrocarbongroup. The term “aromatic hydrocarbon group” refers to a benzene ringoptionally substituted with at least one aliphatic hydrocarbon group.These optional aliphatic hydrocarbon group substituents are preferablyalkyl groups. Examples of cycloaliphatic hydrocarbon groups with 7carbon atoms are cycloheptyl and methyl substituted cyclohexyl. Anexample of an aromatic hydrocarbon group with 7 carbon atoms is methylsubstituted phenyl. Examples of aromatic hydrocarbon groups with 8carbon atoms are xylyl and ethyl substituted phenyl.

Crosslinking efficiency of a crosslinker can be assessed by assessingthe chemical resistance defined and determined as described below.

Whilst the structural units (A) present in the multi-aziridine compoundpresent in the second component of the two-component coating system mayindependently have different m, R′, and/or R″, the structural units (A)present in the multi-aziridine compound are preferably identical to eachother.

The multi-aziridine compound present in the second component of thetwo-component coating system is usually obtained in a composition inwhich, next to the multi-aziridine compound, remaining startingmaterials, side-products and/or solvent used in the preparation of themulti-aziridine compounds may be present. The composition may containonly one multi-aziridine compound as defined in the current inventionbut may also contain more than one multi-aziridine compound as definedin the current invention. Mixtures of multi-aziridine compounds are forexample obtained when a mixture of polyisocyanates as starting materialare used.

The urethane aziridine compound present in the second component of thetwo-component coating system contains from 2 to 6 of the structuralunits (A), preferably from 2 to 4 of the structural units (A), morepreferably 2 or 3 structural units (A). m is an integer from 1 to 6,preferably m is from 1 to 4, more preferably m is 1 or 2 and mostpreferably m is 1.

The molecular weight of the multi-aziridine compound present in thesecond component of the two-component coating system is from 840 to 5000Daltons. The molecular weight of the multi-aziridine compound present inthe second component of the two-component coating system is preferablyat most 3800 Daltons, more preferably at most 3600 Daltons, morepreferably at most 3000 Daltons, more preferably at most 1600 Daltons,even more preferably at most 1200 Daltons. The molecular weight of themulti-aziridine compound present in the second component of thetwo-component coating system is preferably at least 890 Daltons, morepreferably at least 940 Daltons and most preferably at least 1000Daltons. As used herein, the molecular weight of the multi-aziridinecompound is the calculated molecular weight. The calculated molecularweight is obtained by adding the atomic masses of all atoms present inthe structural formula of the multi-aziridine compound. If themulti-aziridine compound is present in a composition comprising morethan one multi-aziridine compound according to the invention, forexample when one or more of the starting materials to prepare themulti-aziridine compound is a mixture, the molecular weight calculationcan be performed for each compound individually present in thecomposition. The molecular weight of the multi-aziridine compoundpresent in the second component of the two-component coating system canbe measured using MALDI-TOF mass spectrometry as described in theexperimental part below.

The multi-aziridine compound present in the second component of thetwo-component coating system comprises one or more linking chainswherein each one of these linking chains links two of the structuralunits A. The linking chains present in the multi-aziridine compoundpreferably consist of from 4 to 300 atoms, more preferably from 5 to250, more preferably from 6 to 100 atoms and most preferably from 6 to20 atoms. The atoms of the linking chains are preferably C andoptionally N, O, S and/or P, preferably C and optionally N and/or O. Thelinking chains are preferably a collection of atoms covalently connectedwhich collection of atoms consists of i) carbon atoms, ii) carbon andnitrogen atoms, or iii) carbon, oxygen and nitrogen atoms.

A linking chain is defined as the shortest chain of consecutive atomsthat links two structural units A. The following drawing shows, for anexample of a multi-aziridine compound according to the invention, thelinking chain between two structural units A.

Any two of the structural units A present in the multi-aziridinecompound present in the second component of the two-component coatingsystem are linked via a linking chain as defined herein. Accordingly,each structural unit A present in the multi-aziridine compound presentin the second component of the two-component coating system is linked toevery other structural unit A via a linking chain as defined herein. Incase the multi-aziridine compound present in the second component of thetwo-component coating system has two structural units A, themulti-aziridine compound has one such linking chain linking these twostructural units. In case the multi-aziridine compound present in thesecond component of the two-component coating system has threestructural units A, the multi-aziridine compound has three linkingchains, whereby each of the three linking chains is linking a structuralunit A with another structural unit A, i.e. a first structural unit A islinked with a second structural unit A via a linking chain and the firstand second structural units A are both independently linked with a thirdstructural unit A via their respective linking chains.

The following drawings show for an example of a multi-aziridine compoundhaving three structural units A, the three linking chains whereby eachone of the three linking chains links two structural units A.

Multi-aziridine compounds present in the second component of thetwo-component coating system with more than two structural units A havea number of linking chains according to the following equation:

LC={(AN−1)×AN)}/2, whereby LC=the number of linking chains and AN=thenumber of structural units A in the multi-aziridine compound. So forexample if there are 5 structural units A in the multi-aziridinecompound, AN=5; which means that there are {(5−1)×5}/2=10 linkingchains.

Preferably, the number of consecutive C atoms and optionally O atomsbetween the N atom of the urethane group in a structural unit A and thenext N atom which is either present in the linking chain or which is theN atom of the urethane group of another structural unit A is at most 9,as shown in for example the following multi-aziridine compoundsaccording to the invention.

The multi-aziridine compound present in the second component of thetwo-component coating system comprises one or more connecting groupswherein each one of these connecting groups connects two of thestructural units A, whereby the connecting groups preferably consist ofat least one functionality selected from the group consisting ofaliphatic hydrocarbon functionality (preferably containing from 1 to 8carbon atoms), cycloaliphatic hydrocarbon functionality (preferablycontaining from 4 to 10 carbon atoms), aromatic hydrocarbonfunctionality (preferably containing from 6 to 12 carbon atoms),isocyanurate functionality, iminooxadiazindione functionality, etherfunctionality, ester functionality, amide functionality, carbonatefunctionality, urethane functionality, urea functionality, biuretfunctionality, allophanate functionality, uretdione functionality andany combination thereof. More preferably, the connecting group is anarray of consecutive functionalities, whereby each functionality isselected from the group consisting of aliphatic hydrocarbonfunctionality (preferably containing from 1 to 8 carbon atoms),cycloaliphatic hydrocarbon functionality (preferably containing from 4to 10 carbon atoms), aromatic hydrocarbon functionality (preferablycontaining from 6 to 12 carbon atoms), isocyanurate functionality,iminooxadiazindione functionality, ether functionality, esterfunctionality, amide functionality, carbonate functionality, urethanefunctionality, urea functionality, biuret functionality, allophanatefunctionality, or uretdione functionality.

The following drawing shows in bold the connecting group for thefollowing example of a multi-aziridine compound present in the secondcomponent of the two-component coating system. In this example, theconnecting group connecting the two structural units A consists of thearray of the following consecutive functionalities: cycloaliphatichydrocarbon functionality 1 (a cyclic C₉H₁₆), aliphatic hydrocarbonfunctionality 2 (a CH₂,) isocyanurate 3 (a cyclic C₃N₃O₃), aliphatichydrocarbon functionality 4 (a CH₂) and a cycloaliphatic hydrocarbonfunctionality 5 (a cyclic C₉H₁₆) and.

Any two of the structural units A present in the multi-aziridinecompound present in the second component of the two-component coatingsystem are preferably connected via a connecting group as definedherein. Accordingly, each structural unit A present in themulti-aziridine compound present in the second component of thetwo-component coating system is preferably connected to every otherstructural unit A with a connecting group as defined in the invention.In case the multi-aziridine compound according to the invention has twostructural units A, the multi-aziridine compound has one such connectinggroup connecting these two structural units. In case the multi-aziridinecompound according to the invention has three structural units A, themulti-aziridine compound has three such connecting groups, whereby eachone of the three connecting groups is connecting a structural unit Awith another structural unit A.

Preferably, the connecting groups consist of at least one functionalityselected from the group consisting of aliphatic hydrocarbonfunctionality (preferably containing from 1 to 8 carbon atoms),cycloaliphatic hydrocarbon functionality (preferably containing from 4to 10 carbon atoms), aromatic hydrocarbon functionality (preferablycontaining from 6 to 12 carbon atoms), isocyanurate functionality,iminooxadiazindione functionality, urethane functionality, ureafunctionality, biuret functionality and any combination thereof. Theconnecting groups preferably contain an isocyanurate functionality, animinooxadiazindione functionality, a biuret functionality, allophanatefunctionality or an uretdione functionality. More preferably, theconnecting groups contain an isocyanurate functionality or animinooxadiazindione functionality. For the sake of clarity, themulti-aziridine compound may be obtained from the reaction product ofone or more suitable compound B and a hybrid isocyanurate such as forexample a HDI/IPDI isocyanurate, resulting in a multi-aziridine compoundwith a connecting group consisting of the array of the followingconsecutive functionalities: a linear C₆H₁₂ (i.e. an aliphatichydrocarbon functionality with 6 carbon atoms), an isocyanuratefunctionality (a cyclic C₃N₃O₃) and

(i.e. a cycloaliphatic hydrocarbon functionality with 9 carbon atoms andan aliphatic hydrocarbon functionality with 1 carbon atom).

The term “aliphatic hydrocarbon functionality” refers to optionallybranched alkyl, alkenyl and alkynyl groups. Whilst the optional branchesof C atoms are part of the connecting group, they are not part of thelinking chain. The term “cycloaliphatic hydrocarbon functionality”refers to cycloalkyl and cycloalkenyl groups optionally substituted withat least one aliphatic hydrocarbon group. Whilst the optional aliphatichydrocarbon group substituents are part of the connecting group, theyare not part of the linking chain. The optional aliphatic hydrocarbongroup substituents are preferably alkyl groups. The term “aromatichydrocarbon functionality” refers to a benzene ring optionallysubstituted with at least one aliphatic hydrocarbon group. The optionalaliphatic hydrocarbon group substituents are preferably alkyl groups.Whilst the optional aliphatic hydrocarbon group substituents are part ofthe connecting group, they are not part of the linking chain.

On the connecting groups, one or more substituents may be present aspendant groups on the connection group, as shown in bold in for examplethe following multi-aziridine compound. These pendant groups are notpart of the connecting groups.

The pendant group preferably contains

in which X, R₇, R₈, n′ and R₁₀ are as described below. In an embodimentof the invention, the multi-aziridine compound comprises one or moreconnecting groups wherein each one of these connecting groups connectstwo of the structural units A, wherein the connecting groups consist of(i) at least two aliphatic hydrocarbon functionality or at least twocycloaliphatic hydrocarbon functionality and (ii) an isocyanuratefunctionality or an iminooxadiazindione functionality, and wherein apendant group is present on a connecting group, whereby the pendantgroup has the following structural formula:

n′ is the number of repeating units and is an integer from 1 to 50,preferably from 2 to 30, more preferably from 5 to 20.X is O or NH, preferably X is O,R₇ and R₈ are independently H or CH₃ in each repeating unit,R₉ is an aliphatic hydrocarbon group, preferably containing from 1 to 8carbon atoms, or a cycloaliphatic hydrocarbon group, preferablycontaining from 4 to 10 carbon atoms, andR₁₀ contains at most 20 carbon atoms and is an aliphatic, cycloaliphaticor aromatic hydrocarbon group or a combination thereof. In a preferredembodiment, one of R₇ and R₈ is H and the other R₇ or R₈ is CH₃. Inanother and more preferred embodiment, R₇ and R₈ are H. R₁₀ preferablyis an aliphatic hydrocarbon group containing from 1 to 20 carbon atoms(preferably CH₃), a cycloaliphatic hydrocarbon group containing from 5to 20 carbon atoms or an aromatic hydrocarbon group containing from 6 to20 carbon atoms. The presence of the pendant group results in adecreased viscosity of the multi-aziridine compound and hence easiermiscibility with the to be crosslinked polymer. In this embodiment, themulti-aziridine compound preferably contains 2 structural units A. Inthis embodiment the connecting group preferably consists of the array ofthe following consecutive functionalities: a first cycloaliphatichydrocarbon functionality, an isocyanurate functionality or animinooxadiazindione functionality, and a second cycloaliphatichydrocarbon functionality, and R₉ is a cycloaliphatic hydrocarbon group,whereby the first and second cycloaliphatic hydrocarbon functionalityand R₉ are identical, more preferably the connecting group consists ofthe array of the following consecutive functionalities: a firstaliphatic hydrocarbon functionality, an isocyanurate functionality or animinooxadiazindione functionality, and a second aliphatic hydrocarbonfunctionality, and R₉ is an aliphatic hydrocarbon group, whereby thefirst and second aliphatic hydrocarbon functionality and R₉ areidentical.

In a preferred embodiment, the multi-aziridine compound according to theinvention contains polyoxyethylene (—O—CH2-CH2-)_(x) group(s) and/orpolyoxypropylene (—O—CHCH3-CH2-)_(x) group(s), preferably in an amountof at least 0.1 wt. %, more preferably at least 6 wt. %, more preferablyat least 10 wt. % and preferably in an amount of less than 45 wt. %,more preferably less than 25 wt. % and most preferably less than 16 wt.%, relative to the multi-aziridine compound. Preferably, themulti-aziridine compound contains polyoxyethylene (—O—CH2-CH2-)_(x)group(s), preferably in an amount of at least 0.1 wt. %, more preferablyat least 6 wt. %, more preferably at least 10 wt. % and preferably in anamount of less than 45 wt. %, more preferably less than 25 wt. % andmost preferably less than 16 wt. %, relative to the multi-aziridinecompound. A multi-aziridine compound containing polyoxyethylene(—O—CH2-CH2-)_(x) group(s) is preferably the reaction product of atleast compound (B), a polyisocyanate and alkoxy poly(ethyleneglycol)(preferably methoxy poly(ethyleneglycol) (MPEG)) and/orpoly(ethyleneglycol). The reaction product can be obtained by reactingat least compound B with the following structural formula:

wherein R′ and R″ are as defined above, the polyisocyanate and alkoxypoly(ethyleneglycol) and/or poly(ethyleneglycol). The reaction productcan also be obtained by reacting the polyisocyanate with alkoxypoly(ethyleneglycol) and/or poly(ethyleneglycol) and reacting theso-obtained compound with compound (B). The reaction product can also beobtained by reacting compound B with the polyisocyanate and reacting theso-obtained compound with alkoxy poly(ethyleneglycol) and/orpoly(ethyleneglycol). The amount of alkoxy poly(ethyleneglycol)(preferably methoxy poly(ethyleneglycol) (MPEG)) and/orpoly(ethyleneglycol) (PEG) chains with a number average molecular weightM_(n) higher than 2200 Daltons, preferably with a M_(n) higher than 1600Daltons in the multi-aziridine compound as defined above is preferablyless than 35 wt. %, more preferably less than 15 wt. %, more preferablyless than 5 wt. % and most preferably 0 wt. %. The methoxypoly(ethyleneglycol) (MPEG) and/or poly(ethyleneglycol) (PEG) chainspresent in the multi-aziridine compound preferably have a M_(n) lowerthan 1100 Daltons, more preferably lower than 770 Daltons and mostpreferably lower than 570 Daltons.

An isocyanurate functionality is defined as

An iminooxadiazindione functionality is defined as

An allophanate functionality is defined as

An uretdione functionality is defined as

A biuret functionality is defined as

In a preferred embodiment of the invention, the connecting groupspresent in the multi-aziridine compound present in the second componentof the two-component coating system consist of the followingfunctionalities: (i) at least one aliphatic hydrocarbon functionalityand/or at least one cycloaliphatic hydrocarbon functionality (ii) and anisocyanurate functionality or iminooxadiazindione functionality orallophanate functionality or uretdione functionality and (iii)optionally at least one aromatic hydrocarbon functionality. Preferably,the connecting groups present in the multi-aziridine compound present inthe second component of the two-component coating system consist of thefollowing functionalities: (i) at least one aliphatic hydrocarbonfunctionality and/or at least one cycloaliphatic hydrocarbonfunctionality and (ii) an isocyanurate functionality oriminooxadiazindione functionality and (iii) optionally at least onearomatic hydrocarbon functionality. A very suitable way of obtainingsuch multi-aziridine compound is reacting compound B with the followingstructural formula:

with a polyisocyanate with aliphatic reactivity. The term “apolyisocyanate with aliphatic reactivity” being intended to meancompounds in which all of the isocyanate groups are directly bonded toaliphatic or cycloaliphatic hydrocarbon groups, irrespective of whetheraromatic hydrocarbon groups are also present. The polyisocyanate withaliphatic reactivity can be a mixture of polyisocyanates with aliphaticreactivity. Compounds based on polyisocyanate with aliphatic reactivityhave a reduced tendency of yellowing over time when compared to asimilar compound but based on polyisocyanate with aromatic reactivity.The term “a polyisocyanate with aromatic reactivity” being intended tomean compounds in which all of the isocyanate groups are directly bondedto a benzene or a naphthalene group, irrespective of whether aliphaticor cycloaliphatic groups are also present. Preferred polyisocyanateswith aliphatic reactivity are 1,5-pentamethylene diisocyanate PDI,1,6-hexamethylene diisocyanate HDI, isophorone diisocyanate IPDI,4,4′-dicyclohexyl methane diisocyanate H12MDI, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate,tetramethylxylene diisocyanate TMXDI (all isomers) and higher molecularweight variants like for example their isocyanurates, oriminooxadiazindiones. More preferred polyisocyanates with aliphaticreactivity are isocyanurates or iminooxadiazindiones of1,5-pentamethylene diisocyanate PDI, of 1,6-hexamethylene diisocyanateHDI, of isophorone diisocyanate IPDI, of 4,4′-dicyclohexyl methanediisocyanate H12MDI, of 2,2,4-trimethyl hexamethylene diisocyanate, of2,4,4-trimethyl hexamethylene diisocyanate, of tetramethylxylenediisocyanate TMXDI. In this embodiment, preferably the connecting groupsconsist of the array of the following consecutive functionalities:aliphatic hydrocarbon functionality, aromatic hydrocarbon functionalityand aliphatic hydrocarbon functionality (for example when using TMXDIfor preparing the multi-aziridine compound) or the connecting groupsconsist of the array of the following consecutive functionalities:cycloaliphatic hydrocarbon functionality, aliphatic hydrocarbonfunctionality and cycloaliphatic hydrocarbon functionality (for examplewhen using H12MDI for preparing the multi-aziridine compound) or morepreferably, the connecting groups consist of the array of the followingconsecutive functionalities: aliphatic hydrocarbon functionality,isocyanurate functionality or iminooxadiazindione functionality, andaliphatic hydrocarbon functionality. Most preferably, in thisembodiment, the connecting group consists of the array of the followingconsecutive functionalities: aliphatic hydrocarbon functionality,isocyanurate functionality, and aliphatic hydrocarbon functionality (forexample when using an isocyanurate of 1,6-hexamethylene diisocyanateand/or an isocyanurate of 1,5-pentamethylene diisocyanate for preparingthe multi-aziridine compound).

The multi-aziridine compound present in the second component of thetwo-component coating system preferably contains at least 5 wt. %, morepreferably at least 5.5. wt. %, more preferably at least 6 wt. %, morepreferably at least 9 wt. %, more preferably at least 12 wt. % andpreferably less than 25 wt. %, preferably less than 20 wt. % of urethanebonds. The multi-aziridine compound present in the second component ofthe two-component coating system preferably has an aziridine equivalentweight (molecular weight of the multi-aziridine compound divided bynumber of aziridinyl groups present in the multi-aziridine compound) ofat least 200, more preferably at least 230 and even more preferably atleast 260 Daltons and preferably at most 2500, more preferably at most1000 and even more preferably at most 500 Daltons.

The multi-aziridine compound can be stabilized if desired with amines,preferably 0.1 to 5, more preferred 0.1 to 2.5 and most preferred 0.1 to1 wt. % of a secondary or tertiary amine. Preferred amines includeammonia, dimethyl ethanol amine, diisopropylamine, isopropanol amine,diethyl ethanol amine, N,N-dimethyl isopropanol amine,3-dimethylamino-1-propanol, 2-[2-(dimethylamino)ethoxy] ethanol, N-ethylmorpholine and dimethyl benzyl amine triethyl amine. Alternatively,alkali hydroxides can be used like for example NaOH, LiOH, KOH as wellas combinations of amines with alkali hydroxides.

The multi-aziridine compound present in the second component of thetwo-component coating system is preferably obtained by reacting at leasta polyisocyanate and a compound B with the following structural formula:

wherein R′ and R″ are as defined above, whereby the molar ratio ofcompound B to polyisocyanate is from 2 to 6, more preferably from 2 to 4and most preferably from 2 to 3, and whereby m is defined above.Reacting the polyisocyanate with compound B may be carried out bybringing equivalent amounts of the polyisocyanate into contact with thecompound B at a temperature in the range of from 0 to 110° C., moresuitable from 20° C. to 110° C., more suitable from 40° C. to 95° C.,even more suitable from 60 to 85° C. in the presence of for example atin catalyst such as for example dibutyltin dilaurate or a bismuthcatalyst such as for example bismuth neodecanoate. A solvent may beused, such as for example dimethylformamide DMF, acetone and/or methylethyl ketone. The polyisocyanate contains at least 2 isocyanate groups,preferably at least 2.5 isocyanate groups on average and more preferablyat least 2.8 isocyanate groups on average. Mixtures of polyisocyanatesmay also be used as starting materials. Preferred polyisocyanates arepolyisocyanates with aliphatic reactivity. The term “a polyisocyanatewith aliphatic reactivity” being intended to mean compounds in which allof the isocyanate groups are directly bonded to aliphatic orcycloaliphatic hydrocarbon groups, irrespective of whether aromatichydrocarbon groups are also present. The polyisocyanate with aliphaticreactivity can be a mixture of polyisocyanates with aliphaticreactivity. Preferred polyisocyanates with aliphatic reactivity are1,5-pentamethylene diisocyanate PDI, 1,6-hexamethylene diisocyanate HDI,isophorone diisocyanate IPDI, 4,4′-dicyclohexyl methane diisocyanateH12MDI, 2,2,4-trimethyl hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, p-tetra-methylxylene diisocyanate (p-TMXDI)and its meta isomer, and higher molecular weight variants like forexample their isocyanurates or iminooxadiazindiones or allophanates oruretdiones. More preferred polyisocyanates with aliphatic reactivity areisocyanurates or iminooxadiazindiones of 1,5-pentamethylene diisocyanatePDI, of 1,6-hexamethylene diisocyanate HDI, of isophorone diisocyanateIPDI, of 4,4′-dicyclohexyl methane diisocyanate H12MD1, of2,2,4-trimethyl hexamethylene diisocyanate, of 2,4,4-trimethylhexamethylene diisocyanate, of tetramethylxylene diisocyanate TMXDI.Even more preferred polyisocyanates with aliphatic reactivity are anisocyanurate or iminooxadiazindione of 1,6-hexamethylene diisocyanate,an isocyanurate or iminooxadiazindione of 1,5-pentamethylenediisocyanate, an isocyanurate or iminooxadiazindione of IPDI. A suitableHDI containing iminooxadiazindione trimer is Desmodur® N3900, obtainablefrom Covestro. A suitable HDI containing allophonate is Desmodur®XP2860, obtainable from Covestro. A suitable HDI containing uretdione isDesmodur® N3400, obtainable from Covestro. Suitable HDI basedisocyanurates trimers can for example be obtained from Covestro(Desmodur® N3600), Vencorex (Tolonate™ HDT LV), Asahi Kasei (Duranate™TPA-100), Evonik (Vestanat® HT 2500/LV) and Tosoh (Coronate® HXR LV).Compound B is preferably 1-(2-hydroxyethyl)ethylenimine (CAS No.1072-52-2).

The multi-aziridine compound present in the second component of thetwo-component coating system is preferably obtained in a processcomprising at least the following step (i):

-   -   (i) Reacting compound B with a polyisocyanate.

The reaction (step (i)) of compound B with the polyisocyanate can becarried out, for example, by bringing equivalent amounts of thepolyisocyanate into contact with the adduct at a temperature in therange of from 20° C. to 110° C., more suitable from 40° C. to 95° C. atatmospheric pressure, in the presence of for example a tin catalyst suchas for example dibutyltin dilaurate.

An example of a preferred multi-aziridine compound according to theinvention is

A further aspect of the current invention is a two-component coatingsystem comprising a first component and a second component each of whichis separate and distinct from each other, wherein the first componentcomprises a carboxylic acid functional polymer dissolved and/ordispersed, preferably dispersed, in an aqueous medium and wherein thesecond component is a crosslinker composition comprising at least onemulti-aziridine compound as defined herein and further comprising atleast one additional component, such as for example remaining startingmaterials, side-products and/or solvent used for preparing themulti-aziridine compound according to the invention. The crosslinkercomposition may contain only one multi-aziridine compound according tothe invention but may also contain more than one multi-aziridinecompound according to the invention. Mixtures of multi-aziridinecompounds are for example obtained when a mixture of polyisocyanates asstarting material to prepare the multi-aziridine are used. After havingobtained the multi-aziridine compound(s), the multi-aziridinecompound(s) may be separated, the reaction product may be used withoutfurther purification or solvent used for preparing the multi-aziridinecompound(s) may be removed from the composition obtained in thepreparation of the multi-aziridine compound(s) of the invention. Theamount of multi-aziridine compounds in the crosslinker composition isusually at least 10 wt. %, usually often at least 15 wt. % and mostoften at least 25 wt. % relative to total amount of the composition. Theamount of multi-aziridine compounds as defined in the current inventionpresent in the crosslinker composition is preferably at least 60 wt. %,more preferably at least 80 wt. % and most preferably at least 99 wt. %,relative to total amount of the crosslinker composition. The molecularweight of the multi-aziridine compounds in the crosslinker compositionis in the range of from 840 Daltons to 5000 Daltons. Preferred molecularweights are as described above and molecular weights of themulti-aziridine compounds are determined using MALDI-TOF-MS as describedin the experimental part herein below. MALDI-TOF-MS meansmatrix-assisted laser desorption ionization time of flight massspectroscopy.

The amount of aziridine functional molecules, present in the crosslinkercomposition, having a molecular weight lower than 250 Daltons, morepreferably lower than 350 Daltons, even more preferably lower than 450Daltons, even more preferably lower than 550 Daltons and even morepreferably lower than 820 Daltons is preferably lower than 1.5 wt. %,more preferably lower than 1 wt. %, even more preferably lower than 0.5wt. % and most preferably lower than 0.1 wt. %, relative to the totalweight of the crosslinker composition, whereby the molecular weight isdetermined using LC-MS as described in the experimental part below.

The average number of aziridinyl groups with structural formula (C)

per aziridinyl-containing molecule in the crosslinker composition ispreferably at least 1.8, more preferably at least 2, more preferably atleast 2.2 and preferably less than 10, more preferably less than 6 andmost preferably less than 4. Most preferably, the average number ofaziridinyl groups per aziridinyl-containing molecule in the crosslinkercomposition is from 2.2 to 3. The calculated average amount of urethanebonds is at least 5 wt. %, more preferably at least 5.5. wt. %, morepreferably at least 6 wt. %, more preferably at least 9 wt. %, morepreferably at least 12 wt. % and preferably and less than 25 wt. %,preferably less than 20 wt. % of urethane bonds, relative to the totalweight of the multi-aziridine compounds present in the crosslinkercomposition.

In view of the potential water sensitivity of the multi-aziridinecompounds as defined herein, the crosslinker composition is preferablyfree of substantial amount of water and more preferably is free ofwater. Free of substantial amount of water means less than 15 wt. %,preferably less than 5 wt. %, more preferably less than 1 wt. % and mostpreferably less than 0.1 wt. %. In view of the potential watersensitivity of the multi-aziridine compounds as defined herein, water ispreferably not deliberately (i.e. small amounts of water may be presentin the compounds used to prepare the multi-aziridine compound(s)according to the invention) be added to the composition.

The multi-aziridine compounds according to the invention preferably havea Brookfield viscosity of at least 10000 mPa·s at 25° C., morepreferably at least 20000, more preferably at least 50000 and preferablyat most 1000000, more preferably at most 500000, and even morepreferably at most 200000 mPa·s at 25° C. As used herein, the Brookfieldviscosity is determined according to ISO 2555-89. In an alternativeembodiment the viscosity of the multi-aziridine was measured with aBrookfield with spindle S63, @ 25° C. at 80% solids in dimethylformamide (DMF). The viscosity as measured according to this method ispreferably in the range of 300 to 20000 mPas, more preferably in therange of from 500 to 12000 and most preferably in the range of from 700to 3000 mPas.

The carboxylic acid functional polymer present in the first component ofthe two-component coating system contains carboxylic acid groups and/orcarboxylate groups which are preferably free of a covalent bond thatblocks these groups to chemically react with the aziridine moietypresent in the multi-aziridine compound. As used herein, the amount ofcarboxylic acid groups present in the carboxylic acid functional polymeris the summed amount of deprotonated and protonated carboxylic acidgroups present in the polymer to be crosslinked, i.e. in the carboxylicacid functional polymer. Thus, the amount of carboxylic acid groupspresent in the carboxylic acid functional polymer is the summed amountof carboxylate groups and carboxylic acid groups present in thecarboxylic acid functional polymer. The polymer to be crosslinkedpreferably comprises carboxylate groups which are at least partiallyneutralized with base. Preferably at least part of the base is avolatile base. Preferably, at least a part of the carboxylic acid groupspresent in the carboxylic acid functional polymer to be crosslinked aresubjected to deprotonation to obtain carboxylate groups. Thedeprotonation is effected by neutralizing the carboxylic acid functionalpolymer with a base. Examples of suitable bases are ammonia, secondaryamines, tertiary amines, LiOH, NaOH and/or KOH. Examples of secondaryamines and tertiary amines are described above. Preferred bases aretertiary amines. Preferred tertiary amines are as described above. Mostpreferred is triethylamine. The pH of the first component is, prior tocombining with the second component, preferably at least 7, morepreferably at least 7.5, even more preferably at least 8 and even morepreferably at least 8.5.

Non-limited examples of crosslinkable carboxylic acid functionalpolymers are vinyl polymers like styrene-acrylics, (meth)acryliccopolymers, vinyl acetate (co)polymers such as for example vinyl acetatevinyl chloride ethylene polymers, polyurethanes, polycondensates likepolyesters, polyamides, polycarbonates and hybrids of any of thesepolymers where at least one of the two polymers have a carboxylic acidfunctionality. The carboxylic acid functional polymer is preferablyselected from the group consisting of polyesters, polycarbonates,polyamides, vinyl polymers, polyacrylates, polymethacrylates,poly(acrylate-co-methacrylate)s, polyurethanes,poly(urethane-co-acrylate)s, poly(urethane-co-methacrylate)s,poly(urethane-co-acrylate-co-methacrylate), polyureas, and mixturesthereof. Preferably by vinyl polymer is meant a polymer comprisingreacted residues of styrene and acrylates and/or methacrylates. In anembodiment of the invention, preferred crosslinkable carboxylic acidfunctional polymers are selected from the group consisting of vinylpolymers, polyacrylates, polymethacrylates,poly(acrylate-co-methacrylate)s and mixtures thereof. In anotherembodiment, the carboxylic acid functional polymer is selected from thegroup consisting of polyurethanes, poly(urethane-co-acrylate)s,poly(urethane-co-methacrylate)s,poly(urethane-co-acrylate-co-methacrylate), polyureas, and mixturesthereof.

The present invention further also relates to a coating compositionobtained by mixing the first and second component of the two-componentcoating system just prior to application of the coating composition,whereby the coating composition comprises aziridinyl groups Q andcarboxylic acid groups in an amount such that the stoichiometric amount(SA) of aziridinyl groups Q on carboxylic acid groups is preferably from0.1 to 2.0, more preferably from 0.2 to 1.5, even more preferably from0.25 to 0.95, most preferably from 0.3 to 0.8. The pH of the coatingcomposition is preferably at least 7.5, more preferably at least 8, morepreferably at least 8.5 and even more preferably at least 9.

The present invention further relates to a substrate having a coatingobtained by (i) applying a coating composition as described above to asubstrate and (ii) drying the coating composition by evaporation ofvolatiles. The drying of the coating composition is preferably affectedat a temperature lower than 160° C., preferably at a temperature lowerthan 90° C., more preferably at a temperature lower than 50° C. and mostpreferably at ambient temperature. The coating composition according tothe invention can be applied to any kind of substrate, such as forexample wood, leather, concrete, textile, plastic, vinyl floors, glass,metal, ceramics, paper, wood plastic composite, glass fiber reinforcedmaterials. The thickness of the dry coating on the substrate ispreferably from 1 to 200 micron, more preferably from 5 to 150 micronand most preferably from 15 to 90 microns. In case the coatingcomposition is an ink composition, the thickness of the dry ink ispreferably from 0.005 to 35 micron, more preferably from 0.05 to 25micron and most preferably from 4 to 15 microns.

A further aspect of the present invention is a multi-aziridine compoundhaving:

-   -   a) from 2 to 6 of the following structural units (A):

-   -   -   whereby        -   m is an integer from 1 to 6, preferably m is 1; and        -   R′ and R″ are both H,

    -   b) one or more connecting groups wherein each one of these        connecting groups connects two of the structural units A and        wherein the connecting groups consist of (i) at least two        aliphatic hydrocarbon functionality or at least two        cycloaliphatic hydrocarbon functionality and (ii) an        isocyanurate functionality or an iminooxadiazindione        functionality, and wherein a pendant group is present on a        connecting group, whereby the pendant group has the following        structural formula:

-   -   -   n′ is the number of repeating units and is an integer from 1            to 50, preferably from 2 to 30, more preferably from 5 to            20,        -   X is O or NH, preferably X is O,        -   R₇ and R₈ are independently H or CH₃ in each repeating unit,        -   R₉ is an aliphatic hydrocarbon group, preferably containing            from 1 to 8 carbon atoms, or a cycloaliphatic hydrocarbon            group, preferably containing from 4 to 10 carbon atoms, and        -   R₁₀ contains at most 20 carbon atoms and is an aliphatic,            cycloaliphatic or aromatic hydrocarbon group or a            combination thereof, and

    -   c) a molecular weight in the range from 840 Daltons to 5000        Daltons.

The presence of the pendant group results in a decreased viscosity ofthe multi-aziridine compound and hence easier miscibility with the to becrosslinked polymer. In a preferred embodiment, one of R₇ and R₈ is Hand the other R₇ or R₈ is CH₃. In another and more preferred embodiment,R₇ and R₈ are H. R₁₀ preferably is an aliphatic hydrocarbon groupcontaining from 1 to 20 carbon atoms (preferably CH₃), a cycloaliphatichydrocarbon group containing from 5 to 20 carbon atoms or an aromatichydrocarbon group containing from 6 to 20 carbon atoms. Saidmulti-aziridine compound preferably contains 2 structural units, and theconnecting group preferably consists of the array of the followingconsecutive functionalities: a first cycloaliphatic hydrocarbonfunctionality, an isocyanurate functionality or an iminooxadiazindionefunctionality, and a second cycloaliphatic hydrocarbon functionality,and R₉ is a cycloaliphatic hydrocarbon group, whereby the first andsecond cycloaliphatic hydrocarbon functionality and R₉ are identical,more preferably the connecting group consists of the array of thefollowing consecutive functionalities: a first aliphatic hydrocarbonfunctionality, an isocyanurate functionality or an iminooxadiazindionefunctionality, and a second aliphatic hydrocarbon functionality, and R₉is an aliphatic hydrocarbon group, whereby the first and secondaliphatic hydrocarbon functionality and R₉ are identical. Preferablysaid multi-aziridine compound contains polyoxyethylene (—O—CH2-CH2-)_(x)group(s) and/or polyoxypropylene (—O—CHCH3-CH2-)_(x) group(s),preferably in an amount of at least 0.1 wt. %, more preferably at least6 wt. %, more preferably at least 10 wt. % and preferably in an amountof less than 45 wt. %, more preferably less than 25 wt. % and mostpreferably less than 16 wt. %, relative to the multi-aziridine compound.Preferably, the multi-aziridine compound contains polyoxyethylene(—O—CH2-CH2-)_(x) group(s), preferably in an amount of at least 0.1 wt.%, more preferably at least 6 wt. %, more preferably at least 10 wt. %and preferably in an amount of less than 45 wt. %, more preferably lessthan 25 wt. % and most preferably less than 16 wt. %, relative to themulti-aziridine compound. A multi-aziridine compound containingpolyoxyethylene (—O—CH2-CH2-)_(x) group(s) is preferably the reactionproduct of at least compound (B), a polyisocyanate and alkoxypoly(ethyleneglycol) (preferably methoxy poly(ethyleneglycol) (MPEG))and/or poly(ethyleneglycol). The reaction product can be obtained byreacting at least compound B with the following structural formula:

wherein R′ and R″ are as defined above, the polyisocyanate and alkoxypoly(ethyleneglycol) and/or poly(ethyleneglycol). The reaction productcan also be obtained by reacting the polyisocyanate with alkoxypoly(ethyleneglycol) and/or poly(ethyleneglycol) and reacting theso-obtained compound with compound (B). The reaction product can also beobtained by reacting compound B with the polyisocyanate and reacting theso-obtained compound with alkoxy poly(ethyleneglycol) and/orpoly(ethyleneglycol). The amount of alkoxy poly(ethyleneglycol)(preferably methoxy poly(ethyleneglycol) (MPEG)) and/orpoly(ethyleneglycol) (PEG) chains with an average molecular weighthigher than 2200 Daltons, preferably with an average molecular weighthigher than 1600 Daltons in the multi-aziridine compound as definedabove is preferably less than 35 wt. %, more preferably less than 15 wt.%, more preferably less than 5 wt. % and most preferably 0 wt. %. Themethoxy poly(ethyleneglycol) (MPEG) and/or poly(ethyleneglycol) (PEG)chains present in the multi-aziridine compound preferably have anaverage molecular weight lower than 1100 Daltons, more preferably lowerthan 770 Daltons and most preferably lower than 570 Daltons. The averagemolecular weight is determined by multiplying the OH functionality ofthe polyol by the equivalent weight of the polyol. The OH functionalityof the polyol is given by the supplier of the polyol. In case the polyolis a diol, the OH functionality is 2. The equivalent weight of thepolyol is calculated by dividing 56100 by the OH number of the polyol.The OH number of the polyol is measured by titration a known mass ofpolyol according to ISO 14900 (2017) and is expressed as mg KOH/gpolyol.

The present invention is now illustrated by reference to the followingexamples. Unless otherwise specified, all parts, percentages and ratiosare on a weight basis.

AV Determination

The acid value on solid material (AV) of a sample is determined based onthe ASTM D1639-90(1996)e1 standard. In the procedure, the sample,dissolved in a good solvent, is titrated with alcoholic potassiumhydroxide solution of a known concentration (KOH). The difference intitration volume between the sample and a blank is the measure of theacid value on solids, according to the following formula:AV=[(Vblank−Vsample)*N_(KOH)*56.1]/(W*S/100), where AV is acid number onsolids in mg KOH/g solid material, Vblank is the volume of KOH solutionused in the blank, Vsample is the volume of KOH solution used in thesample, N_(KOH) is the normality of the KOH solution, W is the sampleweight in grams and S is the solids content of the sample in %.Measurements are performed in duplicate using a potentiometric endpointon a Metrohm 702SM Titrino titrator (accepting the measurement if thedifference between duplicates is <0.1 mg KOH/g solid material).

Chemical Resistance

Chemical resistance testing based on DIN 68861-1:2011-01 standard.

Unless indicated otherwise the chemical resistance is tested as follows:

Coating compositions are composed at 0.9 stoichiometric amounts (SA) oftotal carboxylic acid-reactive functional groups (e.g. aziridine)compared to carboxylic acid functional groups. Coating compositions aretreated as described in the examples, and then cast at 100 μm wet layerthickness using a wire bar applicator. After casting, films were driedfor 1 hour at 25° C., then annealed at 50° C. for 16 hours.Subsequently, a piece of cotton wool was soaked in 1:1Ethanol:demineralized water (by weight) and placed on the film for 60minutes (unless indicated otherwise). After removal of the cotton wooland overnight recovery, the spots were scored according to the followingranks:

-   -   1 Complete coating degradation    -   2 Structural damage to the coating    -   3 Severe marking on coating, visible from multiple directions    -   4 Slight marking on coating, visible from specific angles    -   5 No observed marking or gloss change

Viscosity Measurements:

The apparent viscosity is determined according to ISO 2555:2018. Themeasurement is performed at 23° C. on a Brookfield DVE-LV viscometer(single-cylinder geometry) at 60 rpm. The spindle is selected from S62,S63 or S64, using the lowest numbered spindle (i.e. the largest spindle)that yields a reading between 10% and 100% torque.

Low Molecular Weight Fraction by LC-MS

LC system: Agilent 1290 Infinity II; Detector #1: Agilent 1290 InfinityII PDA; Detector #2: Agilent iFunnel 6550 Q-TOF-MS.

LC-MS analysis for the low molecular weight fraction was performed usingthe following procedure. A solution of ˜100 mg/kg of material wasprepared gravimetrically in methanol and stirred. 0.5 μl of thissolution was injected into a UPLC equipped with ESI-TOF-MS detection.The column used was a 100×2.1 mm, 1.8 um, Waters HSS T3 C18 operated at40° C. Flow rate was 0.5 ml·min⁻¹. Solvents used were 10 mM NH₄CH₃COO inwater set to pH 9.0 with NH₃ (Eluent A), Acetonitrile (B) and THF (C).Two binary gradients were applied from 80/20 A/B to 1/99 A/B in 10minutes and from 1/99 A/B to 1/49/50 A/B/C in 5 minutes, after whichstarting conditions are applied (80/20 A/B). Assuming linear MS responseof all components over all response ranges and an equal ionizationefficiency for all components, Total Ion Current signals wereintegrated. In case of coelution extracted ion chromatograms of thatparticular species were integrated. Dividing the integrated signal of aparticular low-molecular weight peak by the total integrated samplesignal yields the fraction of that low molecular weight species.

MALDI-ToF-MS

All MALDI-ToF-MS spectra were acquired using a Bruker UltraflextremeMALDI-ToF mass spectrometer. The instrument is equipped with a Nd:YAGlaser emitting at 1064 nm and a collision cell (not used for thesesamples). Spectra were acquired in the positive-ion mode using thereflectron, using the highest resolution mode providing accurate masses(range 60-7000 m/z). Cesium Tri-iodide (range 0.3-3.5 kDa) was used formass calibration (calibration method: IAV Molecular Characterisation,code MC-MS-05). The laser energy was 20%. The samples were dissolved inTHF at approx. 50 mg/mL. The matrix used was: DCTB(trans-2-[3-(4-tert-Butylphenyl)-2-methyl-2-propenylidene]malononitrile),CAS Number 300364-84-5. The matrix solution was prepared by dissolving20 mg in 1 mL of THF.

Sodium iodide was used as salt (NaI, CAS Number 7681-82-5); 10 mg wasdissolved in 1 ml THF with a drop of MeOH added. Ratiosample:matrix:salt=10:200:10 (μl), after mixing, 0.5 μL was spot onMALDI plate and allowed to air-dry. The peaks measured in the MALDIspectrum are sodium adducts of multi-aziridine compounds, and in thecontext of this specification the molecular weight (MW) of themulti-aziridine compound corresponds to MW=Obs.[M+M_(cation)]−M_(cation), where Obs. [M+M_(cation)] is the MALDI-TOF MSpeak and M_(cation) is the exact mass of the cation used for making theadduct (in this case sodium with M_(cation)=23.0 Da). Multi-aziridinecompounds can be identified by comparing the MW with the exact molecularmass (i.e. the sum of the—non-isotopically averaged—atomic masses of itsconstituent atoms) of a theoretical structure, using a maximum deviationof 0.6 Da.

Synthesis of P1, a Waterborne Polyurethane

A one-liter flask (equipped with a thermometer and an overhead stirrer),was charged with 29.9 grams of dimethylol propionic acid, 282.1 grams ofa polypropylene glycol with a calculated average molecular weight (M) of2000 Da and an OH-value of 56±2 mg KOH/g polypropylene glycol), 166.5grams of a polypropylene glycol with a calculated average molecularweight (M) of 1000 Da and an OH-value of 112±2 mg KOH/g polypropyleneglycol, and 262.8 grams of isophorone diisocyanate (the averagemolecular weight of each of the polyols is calculated from its OH-valueaccording to the equation: M=2*56100/[OH-value in mg KOH/g polypropyleneglycol). The reaction mixture was placed under N₂ atmosphere, heated to50° C. and subsequently 0.07 g dibutyltin dilaurate were added to thereaction mixture. An exothermic reaction was observed; however propercare was taken in order for the reaction temperature not to exceed 97°C. The reaction was maintained at 95° C. for an hour. The NCO content ofthe resultant polyurethane P1′ was 7.00% on solids as determinedaccording to the ISO 14896 Method A (year 2009) (theoretically 7.44%)and the acid value of the polyurethane P1′ was 16.1±1 mg KOH/gpolyurethane P1′. The polyurethane P1′ was cooled down to 60° C. and18.7 grams of triethylamine were added, and the resulting mixture wasstirred for 30 minutes. Subsequently, an aqueous dispersion of thepolyurethane P1′ (the aqueous dispersion of the polyurethane P1′ isfurther referred to as P1) was prepared as follows: the thus preparedmixture of the polyurethane P1′ and triethylamine was fed—at roomtemperature over a time period of 60 minutes—to a mixture of 1100 gramsof demineralized water, 19.5 grams of nonylphenol ethoxylate (9ethoxylate groups), and 4.0 grams of triethylamine. After the feed wascompleted, the mixture was stirred for additional 5 minutes, andsubsequently 111.2 grams of hydrazine (16 wt % solution in water) wereadded to the mixture. The aqueous dispersion of the polyurethane P1′thus prepared was stirred for an additional 1 h and P1 was obtained.

PREPARATIVE EXAMPLE 2: SYNTHESIS OF WATERBORNE ACRYLIC POLYMER A1

A 2 L four-necked flask equipped with a thermometer and overhead stirrerwas charged with sodium lauryl sulphate (30% solids in water, 18.6 gramsof solution) and demineralized water (711 grams). The reactor phase wasplaced under N₂ atmosphere and heated to 82° C. A mixture ofdemineralized water (112 grams), sodium lauryl sulphate (30% solids inwater, 37.2 grams of solution), methyl methacrylate (209.3 grams),n-butyl acrylate (453.56 grams) and methacrylic acid (34.88 grams) wasplaced in a large feeding funnel and emulsified with an overhead stirrer(monomer feed). Ammonium persulphate (1.75 grams) was dissolved indemineralized water (89.61 grams) and placed in a small feeding funnel(initiator feed). Ammonium persulphate (1.75 grams) was dissolved indemineralized water (10.5 grams), and this solution was added to thereactor phase. Immediately afterwards, 5% by volume of the monomer feedwas added to the reactor phase. The reaction mixture then exothermed to85° C. and was kept at 85° C. for 5 minutes. Then, the residual monomerfeed and the initiator feed were fed to the reaction mixture over 90minutes, maintaining a temperature of 85° C. After completion of thefeeds, the monomer feed funnel was rinsed with demineralized water (18.9grams) and reaction temperature maintained at 85° C. for 45 minutes.Subsequently, the mixture was cooled to room temperature and brought topH=7.2 with ammonia solution (6.25 wt. % in demineralized water), andbrought to 40% solids with further demineralized water.

Genotoxicity Testing

Genotoxicity of examples and comparatives was evaluated by theToxTracker® assay (Toxys, Leiden, the Netherlands). The ToxTracker assayis a panel of several validated Green Fluorescent Protein (GFP)-basedmouse embryonic stem (mES) reporter cell lines that can be used toidentify the biological reactivity and potential carcinogenic propertiesof newly developed compounds in a single test. This methodology uses atwo step-approach.

In the first step a dose range finding was performed using wild-type mEScells (strain B4418). 20 different concentrations for each compound wastested, starting at 10 mM in DMSO as highest concentration and nineteenconsecutive 2-fold dilutions.

Next, genotoxicity of examples and comparatives was evaluated usingspecific genes linked to reporter genes for the detection of DNA damage;i.e. Bscl2 (as elucidated by U.S. Pat. No. 9,695,481B2 and EP2616484B1)and Rtkn (Hendriks et. al. Toxicol. Sci. 2015, 150, 190-203) biomarkers.

Genotoxicity was evaluated at 10, 25 and 50% cytotoxicity in absence andpresence of rat S9 liver extract-based metabolizing systems(aroclor1254-induced rats, Moltox, Boone, N.C., USA). The independentcell lines were seeded in 96-well cell culture plates, 24 h afterseeding the cells in the 96-well plates, fresh ES cell medium containingthe diluted test substance was added to the cells. For each testedcompound, five concentrations are tested in 2-fold dilutions. Thehighest sample concentration will induce significant cytotoxicity(50-70%). In case of no or low cytotoxicity, 10 mM or the maximumsoluble mixture concentration is used as maximum test concentration.Cytotoxicity is determined by cell count after 24 h exposure using aGuava easyCyte 10HT flow cytometer (Millipore).

GFP reporter induction is always compared to a vehicle controltreatment. DMSO concentration is similar in all wells for a particularcompound and never exceeds 1%. All compounds were tested in at leastthree completely independent repeat experiments. Positive referencetreatment with cisplatin (DNA damage) were included in all experiments.Metabolic was evaluated by addition of S9 liver extract. Cells areexposed to five concentrations of the test compound in the presence ofS9 and required co-factors (RegenSysA+B, Moltox, Boone, N.C., USA) for 3h. After washing, cells are incubated for 24 h in fresh ES cell medium.Induction of the GFP reporters is determined after 24 h exposure using aGuava easyCyte 10HT flow cytometer (Millipore). Only GFP expression inintact single cells is determined. Mean GFP fluorescence and cellconcentrations in each well is measured, which is used for cytotoxicityassessment. Data was analyzed using ToxPlot software (Toxys, Leiden, theNetherlands). The induction levels reported are at compoundconcentrations that induce 10%, 25% and 50% cytotoxicity after 3 hexposure in the presence of S9 rat liver extract and 24 h recovery oralternatively after 24 h exposure when not in the presence of S9 ratliver extract.

A positive induction level of the biomarkers is defined as equal to orhigher than a 2-fold induction at at least one of 10, 25 and 50%cytotoxicity in the absence or presence of the metabolizing system ratS9 liver extract; a weakly positive induction as higher than 1.5-foldand lower than 2-fold induction at at least one of 10, 25 and 50%cytotoxicity (but lower than 2-fold at 10, 25 and 50% cytotoxicity) inthe absence or presence of the metabolizing system rat S9 liver extractand a negative as lower than or equal to a 1.5-fold induction at 10, 25and 50% cytotoxicity in the absence and presence of rat S9 liverextract-based metabolizing systems.

Components and Abbreviations Used:

Dimethylformamide (CAS No. 68-12-2) was obtained from Acros Organics (adivision of Thermo Fisher Scientific).

Di(propylene glycol) dimethyl ether (Proglyde DMM, CAS No. 111109-77-4)was obtained from Dow Inc

Trimethylolpropane tris(2-methyl-1-aziridinepropionate), CAS No.64265-57-2, CX-100 was obtained from DSM.

Pentaerythritol tris(3-(1-aziridinyl)propionate), CAS number 57116-45-7was obtained from ABCR.

IPDI (5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane,Desmodur® I, isophorone diisocyanate, CAS No. 4098-71-9) was obtainedfrom Covestro.

Polyethylene Glycol Monomethyl Ether (CAS No. 9004-74-4) with a numberaverage molecular weight of 1000 Da was obtained from Tokyo ChemicalIndustry Co., Ltd.

Vestanat® T 1890/100, an isophorone diisocyanate based isocyanurate (CASNo. 67873-91-0) was obtained from Evonik.

Desmodur® N3600 was obtained from Covestro.

1-methoxy-2-propanol acetate (propylene glycol methyl ether acetate, CASNo. 108-65-6) was obtained from Shell Chemicals.

1-(2-hydroxyethyl)ethyleneimine) (CAS No. 1072-52-2) was obtained fromTokyo Chemical Industry Co., Ltd.

Jeffamine® XTJ-436 (CAS No. 118270-87-4) was obtained from Huntsman

Bismuth neodecanoate (CAS No. 34364-26-6) obtained from TIB chemicals AG(Mannheim, Germany).

Hydrazine (16% solution in water, CAS No. 302-01-2) was obtained fromHoneywell.

Dimethylol propionic acid (DMPA, CAS No. 4767-03-7) was obtained fromPerstop Polyols.

Triethylamine (TEA, CAS No. 121-44-8) was obtained from Arkema

1-propanol (CAS No. 71-23-8) was obtained from Sigma-Aldrich.

Tin 2-ethylhexanoate (CAS No. 301-10-0) was obtained from Sigma-Aldrich.

Dibutyltindilaurate (CAS No. 77-58-7) was obtained from Sigma-Aldrich.

Tegomer® D3403 was obtained from Evonik.

Polypropyleneglycol with a number average molecular weight of 1000 Daand with a number average molecular weight of 2000 Da was obtained fromBASF.

3-Methyl-1-phenyl-2-phospholene-1-oxide (CAS No. 707-61-9) was obtainedfrom Sigma-Aldrich.

1-Butanol (CAS No. 71-36-3) was obtained from Sigma-Aldrich.

Sodium lauryl sulphate (30% solution in water, CAS No. 73296-89-6) wasobtained from BASF.

Methyl methacrylate (CAS No. 80-62-6) was obtained from Lucite Int.

n-Butyl acrylate (CAS No. 141-32-2) was obtained from Dow Chemical.

Methacrylic acid (CAS No. 79-41-4) was obtained from Lucite Int.

Ammonium persulphate (CAS No. 7727-54-0) was obtained from UnitedInitiators.

Ammonia (25% solution in water, CAS No. 1336-21-6) was obtained fromMerck

COMPARATIVE EXAMPLE 1

Comparative Example 1 is trimethylolpropanetris(2-methyl-1-aziridinepropionate), CAS number 64265-57-2 obtainedfrom DSM. Chemical structure is shown below.

For reference, the performance of trimethylolpropanetris(2-methyl-1-aziridinepropionate) as a crosslinker was assessed usingspot tests on coating surfaces, based on procedures from the DIN68861-1:2011-01 standard. For these tests, 0.23 parts of the compoundwere mixed with 0.60 parts of Proglyde™ DMM (dipropylene glycol dimethylether, mixture of isomers) and incubated at 80° C. for 10 minutes underregular agitation. Subsequently, 0.56 parts of the resulting solutionwere added to 20 parts of P1 under continuous stirring, and theresulting mixture was further stirred for 30 minutes. Afterwards, thiscoating composition was filtered and applied to Leneta test cards using100 μm wire rod applicators (Test C1-1). The films were dried for 16hours at 25° C., then annealed at 50° C. for 1 hour and further driedfor 24 hours at 25° C. Subsequently, a piece of cotton wool was soakedin 1:1 EtOH:demineralized water and placed on the film for varioustimespans. After removal of the EtOH and 60 minutes recovery, thefollowing results were obtained (a score of 1 indicates completedegradation of the film, 5 indicates no damage visible):

Ethanol Spot Test

Sample 30 min 60 min 120 min 300 min Test C1-1 4 4 3 3

Genotoxicity Test

Without S9 rat liver extract With S9 rat liver extract concentrationBscl 2 Rtkn Bscl 2 Rtkn → 10 25 50 10 25 50 10 25 50 10 25 50 Comp. Ex.1 1.2 1.5 2.0 1.4 2.0 3.2 1.7 2.3 2.1 3.0 4.3 3.4

The genotoxicity test results shows that the crosslinker of ComparativeExample 1 is genotoxic.

EXAMPLE 1

3.83 grams of 1-(2-hydroxyethyl)ethyleneimine) (Cas No. 1072-52-2,obtained from Tokyo Chemical Industry), 12.21 grams of a poly(ethyleneglycol) monomethyl ether with an average Mn of 1000 Da and 126 grams ofdimethylformamide were charged to a reaction flask equipped with athermometer. The mixture was stirred with a mechanical upper stirrerunder a nitrogen atmosphere and heated to 50° C., after which 0.12 gramsof bismuth neodecanoate was added to the flask and a mixture of 15.00grams of Vestanat® T 1890/100 in 63 grams of dimethylformamide was fedin 30 minutes to a reaction flask. After this, the mixture was heatedfurther to 80° C. Samples were taken at regular intervals and thereaction progress was monitored using a Bruker Alpha FT-IR spectrometeruntil no change in NCO-stretch at 2200-2300 cm⁻¹ was observed.Subsequently, 0.36 grams of 1-butanol were added to the mixture,followed by further reaction to complete disappearance theaforementioned NCO-stretch peak. The solvent was removed in vacuo toobtain an opaque waxy solid. The calculated molecular weights of thetheoretical main components were 927.62 Da (three aziridines), 1797.12(two aziridines, 21 EG repeating units) and 1841.15 Da (two aziridines,22 EG repeating units) chemical structures are shown below.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=950.62Da; Obs. [M+Na+]=950.52 Da.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=1820.12Da; Obs. [M+Na+]=1820.15 Da.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=1864.15Da; Obs. [M+Na+]=1864.20 Da.

The following components with a mass below 820 Da were detected by LC-MSand quantified:

was present in the composition at 0.04 wt %

Performance of the synthesized compound as a crosslinker was assessedusing spot tests on coating surfaces, based on procedures from the DIN68861-1:2011-01 standard. For these tests, 0.75 parts of the compositionwere mixed with 0.75 parts of 1-methoxy-2-propyl acetate and incubatedat 80° C. for 10 minutes under regular agitation. Subsequently, 1.5parts of the resulting solution were added to 10 parts of P1 undercontinuous stirring, and the resulting mixture was further stirred for30 minutes. Afterwards, this coating composition was filtered andapplied to Leneta test cards using 100 μm wire rod applicators (Test1-1). For reference, films were also cast from the same compositionlacking a crosslinker (Test 1-2). The films were dried for 16 hours at25° C., then annealed at 50° C. for 1 hour and further dried fo 24 hoursat 25° C. Subsequently, a piece of cotton wool was soaked in 1:1EtOH:demineralized water and placed on the film for various timespans.After removal of the EtOH and 60 minutes recovery, the following resultswere obtained (a score of 1 indicates complete degradation of the film,5 indicates no damage visible):

Ethanol Spot Test

Sample 30 min 240 min Test 1-1 4 4 Test 1-2 1 1

For further performance tests, 1.0 parts of the composition were mixedwith 1.0 parts of 1-methoxy-2-propyl acetate and incubated at 80° C. for10 minutes under regular agitation. Subsequently, 1.5 parts of theresulting solution were added to 10.5 parts of A1 under continuousstirring, and the resulting mixture was further stirred for 30 minutes.Afterwards, this coating composition was filtered and applied to Lenetatest cards using 100 μm wire rod applicators (Test 1-3). For reference,films were also cast from the same composition lacking a crosslinker(Blank 1-4). The films were dried for 16 hours at 25° C., then annealedat 50° C. for 1 hour and further dried fo 24 hours at 25° C.Subsequently, a piece of cotton wool was soaked in 1:1EtOH:demineralized water and placed on the film for various timespans.After removal of the EtOH and 60 minutes recovery, the following resultswere obtained (a score of 1 indicates complete degradation of the film,5 indicates no damage visible):

Sample 60 min 240 min Test 1-3 3 3 Blank 1-4 1 1

Genotoxicity Test

Without S9 rat liver extract With S9 rat liver extract concentrationBscl 2 Rtkn Bscl 2 Rtkn → 10 25 50 10 25 50 10 25 50 10 25 50 Ex. 1 1.21.3 1.3 1.2 1.1 1.0 1.2 1.3 1.3 1.3 1.1 1.3

The genotoxicity test results show that the crosslinker composition ofExample 1 is non-genotoxic.

COMPARATIVE EXAMPLE 2

15.0 grams of Desmodur N 3600 and 75 grams of dimethylformamide werecharged to a reaction flask equipped with a thermometer. The mixture wasstirred with a mechanical upper stirrer under a nitrogen atmosphere. Themixture was than heated to 50° C., whereafter 6.80 grams of1-(2-hydroxyethyl)ethyleneimine was added. 15 minutes later 0.03 gramsof bismuth neodecanoate was charged to the reaction flask, which wasthen heated further to 60° C. Samples were taken at regular intervalsand the reaction progress was monitored using a Bruker Alpha FT-IRspectrometer until no NCO-stretch at 2200-2300 cm⁻¹ was observed. Thesolvent was removed in vacuo to obtain a clear, slightly yellowishhighly viscous liquid. The calculated molecular weight of thetheoretical main component was 765.47 Da, chemical structure is shownbelow.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+K+]=804.43 Da;Obs. [M+K+]=804.27 Da.

Genotoxicity Test

Without S9 rat liver extract With S9 rat liver extract concentrationBscl 2 Rtkn Bscl 2 Rtkn → 10 25 50 10 25 50 10 25 50 10 25 50 Comp. Ex.2 1.1 1.3 1.4 1.7 2.4 2.8 1.4 1.9 1.9 2.0 3.4 3.0

The genotoxicity test results show that the reaction product of Comp Ex2 is genotoxic.

EXAMPLE 2

3.83 grams of 1-(2-hydroxyethyl)ethyleneimine) (Cas No. 1072-52-2,obtained from Tokyo Chemical Industry), 12.27 grams of Jeffamine®XTJ-436 (CAS number 118270-87-4, obtained from Huntsman) and 126 gramsof dimethylformamide were charged to a reaction flask equipped with athermometer. The mixture was stirred with a mechanical upper stirrerunder a nitrogen atmosphere and heated to 50° C., after which 0.10 gramsof bismuth neodecanoate was added to the flask and a mixture of 15.00grams of Vestanat® T 1890/100 in 95 grams of dimethylformamide was fedin 30 minutes to a reaction flask. After this, the mixture was heatedfurther to 80° C. Samples were taken at regular intervals and thereaction progress was monitored using a Bruker Alpha FT-IR spectrometeruntil no change in NCO-stretch at 2200-2300 cm⁻¹ was observed.Subsequently, 0.36 grams of 1-butanol were added to the mixture,followed by further reaction to complete disappearance theaforementioned NCO-stretch peak. The solvent was removed in vacuo toobtain an opaque waxy solid. The calculated molecular weights of thetheoretical main components were 927.62 Da (three aziridines), 1814.29Da (two aziridines, 13 PO repeating units) and 1827.33 Da (twoaziridines, 14P0 repeating units) chemical structures are shown below.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=950.62Da; Obs. [M+Na+]=950.52 Da.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=1837.28Da; Obs. [M+Na+]=1837.15 Da.

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=1895.32Da; Obs. [M+Na+]=1895.15 Da.

The following components with a mass below 820 Da were detected by LC-MSand quantified:

was present in the composition at 0.10 wt %.

Performance of the synthesized compound as a crosslinker was assessedusing spot tests on coating surfaces, based on procedures from the DIN68861-1:2011-01 standard. For these tests, 1.03 parts of the compositionwere mixed with 0.26 parts of dimethylformamide and incubated at 80° C.for 10 minutes under regular agitation. Subsequently, 1.29 parts of theresulting solution were added to 15 parts of P1 under continuousstirring, and the resulting mixture was further stirred for 30 minutes.Afterwards, this coating composition was filtered and applied to Lenetatest cards using 100 μm wire rod applicators (Test 2-1). For reference,films were also cast from the same composition lacking a crosslinker(Test 2-2). The films were dried for 16 hours at 25° C., then annealedat 50° C. for 1 hour and further dried fo 24 hours at 25° C.Subsequently, a piece of cotton wool was soaked in 1:1EtOH:demineralized water and placed on the film for various timespans.After removal of the EtOH and 60 minutes recovery, the following resultswere obtained (a score of 1 indicates complete degradation of the film,5 indicates no damage visible):

Ethanol Spot Test

Sample 30 min 240 min Test 2-1 4 3 Test 2-2 1 1

For further performance tests, 1.45 parts of the composition were mixedwith 0.39 parts of dimethylformamide and incubated at 80° C. for 10minutes under regular agitation. Subsequently, 1.84 parts of theresulting solution were added to 10.5 parts of A1 under continuousstirring, and the resulting mixture was further stirred for 30 minutes.Afterwards, this coating composition was filtered and applied to Lenetatest cards using 100 μm wire rod applicators (Test 2-3). For reference,films were also cast from the same composition lacking a crosslinker(Blank 2-4). The films were dried for 16 hours at 25° C., then annealedat 50° C. for 1 hour and further dried fo 24 hours at 25° C.Subsequently, a piece of cotton wool was soaked in 1:1EtOH:demineralized water and placed on the film for various timespans.After removal of the EtOH and 60 minutes recovery, the following resultswere obtained (a score of 1 indicates complete degradation of the film,5 indicates no damage visible):

Sample 60 min 240 min Test 2-3 3 3 Blank 2-4 1 1

Genotoxicity Test

Without S9 rat liver extract With S9 rat liver extract concentrationBscl 2 Rtkn Bscl 2 Rtkn → 10 25 50 10 25 50 10 25 50 10 25 50 Ex. 2 1.21.5 1.6 1.4 1.3 1.2 1.1 1.6 1.7 1.4 1.3 1.2

The genotoxicity test results show that the crosslinker composition ofExample 2 only has weakly positive induced genotoxicity.

COMPARATIVE EXAMPLE 3

Comparative Example 3 is pentaerythritoltris(3-(1-aziridinyl)propionate), CAS number 57116-45-7, obtained fromABCR. Chemical structure is shown below.

Genotoxicity Test

Without S9 rat liver extract With S9 rat liver extract concentrationBscl 2 Rtkn Bscl 2 Rtkn → 10 25 50 10 25 50 10 25 50 10 25 50 Comp. Ex.3 1.2 1.4 2.1 1.2 1.7 3.5 1.1 1.5 2.3 1.3 2.1 4.3

The genotoxicity test results show that the crosslinker of ComparativeExample 3 is genotoxic.

COMPARATIVE EXAMPLE 4 (EXAMPLE 5 U.S. Pat. No. 5,258,481)

Under a nitrogen atmosphere, 21.3 g (0.354 mole) of 1-propanol was addedover a period of 6 hours to 78.7 g Isophorone diisocyanate (IPDI) and0.01 g tin 2-ethyl hexanoate at 20-25° C., while stirring. Afterstanding overnight, 196.3 g (0.883 mole) IPDI, 74.1 g (0.0628 mole)Tegomer D3403 and 2.4 g 3-Methyl-1-phenyl-2-phospholene-1-oxide wereadded. The mixture was heated while stirring to 150° C. The mixture waskept at 150° C. until NCO content was 7.0 wt %. Mixture was cooled to80° C. and 333 g methoxypropyl acetate was added. A solution ofisocyanate functional polycarbodiimide was obtained with a solid contentof 50.6 wt % and an NCO content of 7.0 wt % on solids.

To 100 g of this isocyanate functional polycarbodiimide was added 7.0 g1-(2-hydroxyethyl)ethyleneimine (0.08 mole). One drop of dibutyltindilaurate was added. The mixture was heated to 80° C. while stirring.The mixture was kept at 80° C. for 1 hour. FTIR showed a small remainingisocyanate signal, which disappeared after a few days. The solution wasfurther diluted with 8.0 g methoxypropyl acetate, resulting in a yellowsolution with a solid content of 50.4 wt %. This aziridine functionalcarbodiimide contains 3.2 meq acid reactive groups (i.e aziridine andcarbodiimide functionality) per gram solids. The generalized structureof this carbodiimide is depicted below.

in which a, b and c indicates repeating units.

This generalized structure was confirmed by MALDI-TOF-MS, an example isshown below:

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=2043.34Da; Obs. [M+Na+]=2043.32 Da.

Genotoxicity Test Results:

Without S9 rat liver extract With S9 rat liver extract concentrationBscl 2 Rtkn Bscl 2 Rtkn → 10 25 50 10 25 50 10 25 50 10 25 50 Comp. Ex.4 1.3 1.5 1.6 1.2 1.9 1.9 1.2 1.4 1.5 2.0 2.0 1.8

The genotoxicity test results demonstrate that the crosslinker ofcomparative example 4 is genotoxic.

1. A two-component coating system comprising a first component and asecond component each of which is separate and distinct from each other,wherein the first component comprises a carboxylic acid functionalpolymer dissolved and/or dispersed in an aqueous medium, whereby thecarboxylic acid functional polymer contains carboxylic acid groupsand/or carboxylate groups, and the second component comprises amulti-aziridine compound having: a) from 2 to 6 of the followingstructural units (A):

whereby m is an integer from 1 to 6, and R′ and R″ are both H; b) one ormore linking chains wherein each one of these linking chains links twoof the structural units A, whereby a linking chain is the shortest chainof consecutive atoms that links two structural units A; c) one or moreconnecting groups whereby each one of the connecting groups connects twoof the structural units A and whereby the connecting groups consist ofat least one functionality selected from aliphatic hydrocarbonfunctionality, cycloaliphatic hydrocarbon functionality, aromatichydrocarbon functionality, isocyanurate functionality,iminooxadiazindione functionality, ether functionality, esterfunctionality, amide functionality, carbonate functionality, urethanefunctionality, urea functionality, biuret functionality, allophanatefunctionality, uretdione functionality and any combination thereof; andd) a molecular weight in the range from 840 Daltons to 5000 Daltons,wherein the molecular weight is determined using MALDI-TOF massspectrometry as described in the description.
 2. The two-componentcoating system according to claim 1, wherein m is
 1. 3. Thetwo-component coating system according to claim 1, wherein themulti-aziridine compound contains 2 or 3 structural units (A).
 4. Thetwo-component coating system according to claim 1, wherein the linkingchains consist of from 4 to 300 atoms, more preferably from 5 to 250 andmost preferably from 6 to 100 atoms and the linking chains are acollection of atoms covalently connected which collection of atomsconsists of i) carbon atoms, ii) carbon and nitrogen atoms, or iii)carbon, oxygen and nitrogen atoms.
 5. The two-component coating systemaccording to claim 1, wherein the number of consecutive C atoms andoptionally O atoms between the N atom of the urethane group in astructural unit A and the next N atom which is either present in thelinking chain or which is the N atom of the urethane group of anotherstructural unit A is at most
 9. 6. The two-component coating systemaccording to claim 1, wherein the multi-aziridine compound has amolecular weight of from 840 to 3800 Daltons.
 7. The two-componentcoating system according to claim 1, wherein the connecting groups ofthe multi-aziridine compound consist of at least one functionalityselected from: aliphatic hydrocarbon functionality, cycloaliphatichydrocarbon functionality, aromatic hydrocarbon functionality,isocyanurate functionality, iminooxadiazindione functionality, urethanefunctionality, urea functionality, biuret functionality and anycombination thereof.
 8. The two-component coating system according toclaim 1, wherein the multi-aziridine compound comprises one or moreconnecting groups wherein each one of these connecting groups connectstwo of the structural units A, wherein the connecting groups consist of(i) at least two aliphatic hydrocarbon functionality or at least twocycloaliphatic hydrocarbon functionality and (ii) an isocyanuratefunctionality or an iminooxadiazindione functionality, and wherein apendant group is present on a connecting group, whereby the pendantgroup has the following structural formula:

n′ is the number of repeating units and is an integer from 1 to 50,preferably from 2 to 30, more preferably from 5 to
 20. X is O or NH, R₇and R₈ are independently H or CH₃ in each repeating unit, R₉ is analiphatic hydrocarbon group, preferably containing from 1 to 8 carbonatoms, or a cycloaliphatic hydrocarbon group, preferably containing from4 to 10 carbon atoms, and R₁₀ contains at most 20 carbon atoms and is analiphatic, cycloaliphatic or aromatic hydrocarbon group or a combinationthereof.
 9. The two-component coating system according to claim 8,wherein X is O and R₇ and R₈ are H.
 10. The two-component coating systemaccording to claim 8, wherein the multi-aziridine compound contains 2structural units (A).
 11. The two-component coating system according toclaim 10, wherein the connecting group consists of the array of thefollowing consecutive functionalities: a first aliphatic hydrocarbonfunctionality, an isocyanurate functionality or an iminooxadiazindionefunctionality, and a second aliphatic hydrocarbon functionality, and R₉is an aliphatic hydrocarbon group, whereby the first and secondaliphatic hydrocarbon functionality and R₉ are identical.
 12. Thetwo-component coating system according to claim 1, wherein themulti-aziridine compound contains polyoxyethylene (—O—CH2-CH2-)_(x)group(s) in an amount of at least 0.1 wt. %, preferably at least 6 wt.%, more preferably at least 10 wt. % and in an amount of less than 45wt. %, more preferably less than 25 wt. % and most preferably less than16 wt. %, relative to the multi-aziridine compound.
 13. Thetwo-component coating system according to claim 1, wherein themulti-aziridine compound is obtained by reacting at least apolyisocyanate and a compound B with the following structural formula:

whereby the molar ratio of compound B to polyisocyanate is from 2 to 6,more preferably from 2 to 4 and most preferably from 2 to 3, and wherebym, R′, and R″, are defined in previous claims.
 14. The two-componentcoating system according to claim 13, wherein the polyisocyanate is apolyisocyanate with aliphatic reactivity in which all of the isocyanategroups are directly bonded to aliphatic or cycloaliphatic hydrocarbongroups, irrespective of whether aromatic hydrocarbon groups are alsopresent.
 15. The two-component coating system according to claim 1,wherein the second component is a crosslinker composition comprising atleast one multi-aziridine compound as defined in any of the precedingclaims and further comprising at least one additional component.
 16. Thetwo-component coating system according to claim 15, wherein the amountof aziridine functional molecules having a molecular weight lower than820 Daltons is lower than 1.5 wt. %, preferably lower than 1 wt. %,relative to the total weight of the crosslinker composition, whereby themolecular weight is determined using LC-MS as described in thedescription, and wherein the crosslinker composition contains less than5 wt. % of water.
 17. A substrate having a coating obtained by (i)applying a coating composition obtained by mixing the first and secondcomponent of the two-component system according to claim 1 to asubstrate and (ii) drying the coating composition by evaporation ofvolatiles.
 18. A multi-aziridine compound having: a) from 2 to 6 of thefollowing structural units (A):

whereby m is an integer from 1 to 6; and R′ and R″ are both H, b) one ormore connecting groups wherein each one of these connecting groupsconnects two of the structural units A and wherein the connecting groupsconsist of (i) at least two aliphatic hydrocarbon functionality or atleast two cycloaliphatic hydrocarbon functionality and (ii) anisocyanurate functionality or an iminooxadiazindione functionality, andwherein a pendant group is present on a connecting group, whereby thependant group has the following structural formula:

n′ is the number of repeating units and is an integer from 1 to 50,preferably from 2 to 30, more preferably from 5 to 20, X is O or NH, R₇and R₈ are independently H or CH₃ in each repeating unit, R₉ is analiphatic hydrocarbon group, preferably containing from 1 to 8 carbonatoms, or a cycloaliphatic hydrocarbon group, preferably containing from4 to 10 carbon atoms, and R₁₀ contains at most 20 carbon atoms and is analiphatic, cycloaliphatic or aromatic hydrocarbon group or a combinationthereof, and c) a molecular weight in the range from 840 Daltons to 5000Daltons, wherein the molecular weight is measured using MALDI-TOF massspectrometry.
 19. The multi-aziridine compound according to claim 18,wherein X is O and R₇ and R₈ are independently H.
 20. Themulti-aziridine compound according to claim 18, wherein themulti-aziridine compound contains 2 structural units (A).
 21. Themulti-aziridine compound according to claim 18, wherein the connectinggroup consists of the array of the following consecutivefunctionalities: a first aliphatic hydrocarbon functionality, anisocyanurate functionality or an iminooxadiazindione functionality, anda second aliphatic hydrocarbon functionality, and R₉ is an aliphatichydrocarbon group, whereby the first and second aliphatic hydrocarbonfunctionality and R₉ are identical.